Your question is valid. I traded in a flashed RT that has been up to 9,100 rpm. I was in a cold sweat as the BUDS were hooked up. A puzzled tech called over another tech as they BOTH looked at something. Later, I got the courage to ask the techs. He said they could see some misc error codes that happened during my ECU testing for Monster fuel. They also could see the 9,100 rpm and thought it must be incorrect. I told them a young child was sitting on my bike while it was idling and pulled the throttle wide open until the rev limit stopped it. They said that made sense as it would free spin from energy past the rev limit.
So it seems the flash itself is NOT detectable.
Having close to 20,000 miles on the stage one flash with two different Spyders I feel that there is not any power advantage or NEED to shift above the designed red line of our Spyders. I rarely have any need to shift above 7,200 rpm. To me it feels 7,200 rpm is where power and torque give my F3L all it needs to get flying.
I agree with jcthorne that it gets more confusing when trying to get a technical answer.
But, the proof is in the reviews that really big gains are happening across the entire rpm range. The Dyno chart that was shared with me show stock being about 95 hp at the rear wheel, stage 1 about 118 hp and stage 2 about 122 hp.
Hope this info helps.
Dennis
Ive only had mine out once with the Flashed ECU------- It's great and the best proformance mod for the $$$. 
